Digital control system

Abstract

A solid state, digital control system is disclosed for individually timing and sequentially operating a number of electrically controllable devices such as remote control valves and pumps for irrigation systems. In one embodiment, the digital control system comprises clock circuits (10) which produce at least two pulses, a first or daily pulse produced at the beginning of a day and a second or alarm pulse produced at a preselected time. The daily pulse is counted by a first counter (20) and the alarm pulse is counted by a second counter (22). A plurality of outputs (24) are individually actuated on successive days by first counter (20) and are selectively applied by controllable switches (131-144) to an inhibit input (32) of second counter (22) whenever the sequential operation of the devices is not desired on a particular day. A plurality of output control circuits (38) are individually connected to the outputs (26) of second counter (22) and controlled by the court therein. Each of the output circuits (38) is connectable to a device to be controlled thereby. Also connected to outputs (26) is control logic (42) that is also responsive to the count in second counter (22). Control logic (42) in turn controls the generation of a pulse by a pulse generator (44) after a selectable time delay that can differ for each device being controlled. The output of a pulse generator (44) is connected to a clock input of second counter (22), thereby changing the count therein. Thus the device controlled by output control circuits (38) is changed after the preselected operation time of the previously controlled device has expired.

We claim: 
     
       1. An electronic controller for periodically controlling the operation of a plurality of devices comprising: a clock circuit means for providing at least a first timing pulse once a day at the same time at a first clock output thereof, and a second timing pulse at a preselected time at a second clock output thereof;   a first counter means, having a first input connected to said first clock output and an output, for counting the input pulses and providing an output signal representative of the count therein at said output thereof;   a second counter means, having a first input connected to said second clock output, a second input, a clock input for advancing the count in said second counter means, and an output, for counting the input pulses and providing an output signal at said output representative of the count therein;   an output control circuit connected to said second counter means output and having a plurality of operating circuits each adapted to control the operation of a device and each selected and controlled in turn in a timed sequence based on the count in said second counter means;   means for selectively applying the output signal of said first counter means based upon said first count to said second input of said second counter means for controlling the operation thereof; and   means for providing a pulse to said clock input of said second counter means after a variable preselected time delay from the selection of the device, said provided pulse thereby advancing the count in said second counter and changing the selected control circuit.   
     
     
       2. An electronic controller as claimed in claim 1 and further including means for causing said timed sequence to repeat after the completion thereof. 
     
     
       3. An electronic controller as claimed in claim 1 and further including means responsive to rain for inhibiting the operation of the plurality of controlled devices when rain is detected. 
     
     
       4. An electronic controller as claimed in claim 1 and further including means for delaying the operation of the next device to be operated for a predetermined, selectable time delay after the operation of the previous device. 
     
     
       5. An electronic controller as claimed in claim 1 wherein said pulse providing means comprises a pulse generator, the output of which is connected to said clock input of said second counter means and control logic means for causing said pulse generator to produce an output, said control logic means comprising a plurality of time delay means and means for selecting a particular time delay means based on the count in said second counter means. 
     
     
       6. An electronic controller as claimed in claim 1 wherein said pulse providing means comprises a plurality of switch means corresponding to the number of devices being controlled so that the individual operation of each device can be separately determined, said switch means having a plurality of selectable outputs, a logic circuit connected to the outputs of said switch means for producing a first number signal; counter means connected to said clock for receiving periodic timing therefrom and for producing a second number signal; and comparator means for comparing said first and said second number signals and for producing an output signal at a predetermined comparison, said output signal being delivered to the clock input of said second counter means.